1. Technical Field
The present invention relates to a solid-state image capturing device and a manufacturing method for the same.
2. Related Art
Heretofore, solid-state image capturing devices such as CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) image sensors, for example, have been used in electronic devices provided with an image capturing function, such as digital still cameras and digital video cameras.
For example, a CMOS image sensor is configured in each pixel to transfer a charge from a light-receiving element (photodiode) to a floating diffusion layer, and to read out the potential of the floating diffusion layer using a source follower circuit.
For example, JP-A-8-316460 discloses that by providing a p−-type impurity layer whose impurity concentration is sufficiently lower than that of a p-well, the width of a depletion layer in a p-n junction is increased and the capacitance of a floating diffusion layer is reduced. Also, JP-A-8-316460 discloses that by reducing the capacitance of the floating diffusion layer, variation in the potential of the floating diffusion layer is increased and the charge detection sensitivity is increased.
With a solid-state image capturing device in which a photodiode and a floating diffusion layer are formed in the same substrate, the photodiode temporarily stores charges that are generated due to being irradiated with light. It is preferable that the amount of charge that can be stored in the photodiode (maximum storage charge amount) is large. If the maximum storage charge amount of the photodiode decreases, the maximum signal level that can be read out by the source follower circuit with respect to the light used for irradiation decreases, incurring a decrease in the dynamic range in some cases.